This invention comprises an improvement over balanced steerable power transmissions disclosed in my U.S. Pat. Nos. 3,750,616 and 3,851,614. The subject matter of the aforementioned patents and applications is hereby incorporated by reference.
In the steerable transmissions of the above-identified patents there are input and output shafts with the output shaft mounted in a housing which is steerable. This permits the direction of the output shaft to be changed independently of the direction of rotation of the input shaft. Such an arrangement can be used, for example, for steering a boat, thereby gaining benefits of both an inboard and an outboard arrangement. These transmissions can be somewhat cumbersome and have appreciable drag since a large housing is rotated.
It is desirable to provide an arrangement where the transmission housing is essentially fixed and a steerable sleeve or the like can be pivoted about an axis coaxial with the output shaft. This permits a relatively smaller structure to be pivoted. It is desirable that the sleeve be steerable with substantially no net torque; that is, with essentially the same torque required to pivot the sleeve in either direction, regardless of the direction or speed of rotation of the output shaft.
This not only makes the steerable transmission quite suitable for use in small boats, it can significantly increase the fields in which the transmission is useful. It can be employed in land and air vehicles, construction equipment, wind generators, and a broad variety of other applications limited only by the ingenuity of the user.
It can be desirable to minimize the size of the transmission and to provide means for steering embodied in the transmission instead of operating on an external mechanism. It is also desirable to maintain symmetry of the parts used for building the transmission for minimizing the type of parts stocked to provide economies of scale in purchasing or making parts. It is also desirable to be able to readily adapt the transmission in manufacture to provide different gear ratios between the input and output.